The present invention relates to a displacement control valve which constitutes a refrigerant circulation path and is used in a variable displacement compressor capable of changing a refrigerant displacement on the basis of a pressure in a control pressure zone within the compressor.
This kind of variable displacement compressor forms a part of the circulation path in which a refrigerant gas corresponding to a fluid circulates, for example, in an air conditioner for a vehicle. The variable displacement compressor is provided with a control pressure chamber (a control pressure zone), and a swash plate is arranged in the control pressure chamber in such a manner that a inclination thereof can be changed. The inclination of the swash plate is changed in correspondence to a pressure in the control pressure chamber. In this variable displacement compressor, if the pressure in the control pressure chamber becomes higher, and an inclination angle of the swash plate becomes smaller, a stroke of pistons becomes smaller, and a displacement of the refrigerant gas is reduced. On the other hand, if the pressure in the control pressure chamber becomes lower, and the inclination angle of the swash plate becomes larger, the stroke of the pistons becomes larger, and the displacement of the refrigerant gas is increased.
To the variable displacement compressor, there are connected a gas passage for supplying the refrigerant gas to the control pressure chamber from the discharge pressure zone, and a displacement control valve for opening and closing the gas passage. The displacement control valve is provided with a solenoid portion, and a pressure sensing means for actuating a valve body in correspondence to the pressure of the refrigerant gas. The solenoid portion is provided with a tubular fixed iron core, and a movable iron core and a rod coupled to the movable iron core are inserted to the fixed iron core.
The displacement control valve is provided with a valve chamber within a housing, and a valve body is arranged in the valve chamber so as to be capable of reciprocating. The valve chamber is provided with a guide portion for moving the valve body along an axis of the valve chamber. The valve body is fixed to an end portion in an opposite side to the movable iron core in the rod. In this displacement control valve, if an electromagnetic force is generated in the solenoid portion, the valve body reciprocates together with the rod. The valve portion of the valve body selectively contacts and separate from a valve seat of the valve chamber on the basis of a reciprocation of the valve body. Accordingly, a valve hole and the gas passage are selectively opened and closed so as to adjust a supply amount of the refrigerant gas from the discharge pressure zone to the control pressure chamber.
For example, a displacement control valve disclosed in Japanese Laid-Open Patent Publication No. 2003-322086 is structured such that no excessive pressure is applied to the pressure sensing means at a time when the valve body is opened, by introducing a pressure in a suction pressure zone into the valve body. In this case, in order to introduce the pressure in the suction pressure zone into the valve body, an open passage is formed within the rod and the valve body in such a manner as to communicate with the suction pressure zone.
In this displacement control valve, in order to smoothly move the rod and the valve body, a clearance is formed between the rod and the fixed iron core, and between the valve body and the guide portion. There is a case that the clearance allows the valve body and the rod to tilt with respect to an axis of the valve chamber. If the valve hole is closed in this state, a problem happens that a gap is formed between the valve body and the valve seat and the refrigerant gas leaks from the gap. Particularly, in the case that the open passage is formed within the rod and the valve body, it is necessary to make diameters of the rod and the valve body large. Accordingly, the gap between the valve body and the valve seat becomes large, and a leaking amount of the refrigerant gas from the gap is increased.